1. Field of the Invention
The present invention relates generally to the field of robotics and more particularly to a robotic joint (wrist or shoulder joint) having pivoted semicircular links and a split equator which allows for a scissoring action between the rotation axes of these pivoted links about a center point, all this to produce a relative pointing action between a pair of arms.
2. Description of the Related Art
The Humen U.S. Pat. No. 3,973,469 shows a power transmission mechanism which utilizes a spherical member and can be back-driven through fluid pressure to actuate a ball in socket joint which can serve as a robot wrist.
The Wells U.S. Pat. No. 4,045,958 shows a hydraulically actuated multi-directional positioning system which can serve as a robot wrist.
The Rosheim U.S. Pat. Nos. 4,194,437 and 4,2996,681 both describe hydraulic servo mechanisms which can be used as robot wrists.
The Dien U.S. Pat. No. 4,628,765 describes the use of slotted semi-circular links to in order to actuate a ball in socket joint that can serve as a robot wrist. The system produces less than a hemisphere of dextrous workspace.
The Ikeda U.S. Pat. No. 4,683,406 describes a wrist joint assembly which is said to be similar to the human forehand.
The Taylor U.S. Pat. No. 4,073,201 describes a wrist joint with three mutually intersecting axes of rotation. The mechanism has a unique C-shape which allows movement of the roll axis (i.e., pointing) through an arc in excess of 180.degree..
The Rosheim U.S. Pat. Nos. 4,686,866, 4,723,460, 4,729,253, 5,036,724, and 5,239,883 present non-spherical robot wrists with singularity-free workspaces.
The Kimura U.S. Pat. No. 4,574,655 uses three mutually intersecting axes of rotation and a system of bevel gears and drive shafts to actuate these axes.
The Stackhouse U.S. Pat. No. 4,068,536 also shows a geared three axis wrist which uses concentric drive shafts to transmit the rotations to the axes.
The Fletcher U.S. Pat. No. 4,068,763 presents a geared three axis wrist which claims a fine positioning ability.
The Rosheim U.S. Pat. No. 4,804,220 presents a tendon-actuated and non-spherical robot wrist with a singularity-free workspace.
The Rosheim U.S. Pat. No. 4,821,594 presents a non-spherical robot joint with a singularity-free workspace.
The Rosheim U.S. Pat. No. 4,911,033 presents a complete robot manipulator which incorporates a non-spherical robot joint for the wrist and another for the shoulder of a manipulator.
The Duta and Stanisic U.S. Pat. No. 4,878,393 shows a singularity-free and spherical robot wrist joint with a solid equator which does not permit a scissoring action between the axes of rotation of the pivoted semicircular links.
With the exception of the Rosheim patents and the Duta and Stanisic patent, all of the above-described conventional robot joints are capable of less than a hemisphere of singularity-free workspace. The Rosheim patents all contain non-spherical arrangements and the Duta and Stanisic patent contains a solid equator which will not permit a scissoring action between the axes of rotation of the pivoted semi-circular links about the center point of the joint.